Molecular Cloning and Sequence Analysis of cDNA Coding for the Precursor of the Human Salivary Proline-Rich Peptide P-B1

cDNA coding for the human salivary proline-rich peptide P-B was amplified by polymerase chain reaction using human submaxillary gland cDNA as the template and d(deoxy)T25 as the primer for both strands. The amplified cDNA of 0.8 kbp encodes a hydrophobic signal sequence of 22 amino acid residues and the complete sequence of P-B (57 amino acids). The determined nucleotide sequence of P-B cDNA indicates that P-B is a mature full-size protein and not the enzymic degradation product of a larger protein. The gene coding for P-B is not a member of the proline-rich protein gene family characterized previously.